Tube plate for hot gas coolers

ABSTRACT

A tube plate for heat exchangers, particularly for hotgas coolers, wherein the gas inlet is exposed to gas temperatures exceeding 500* C. at high gas velocities, and wherein the gas inlet portions of the tubes conveying the gas that is to be cooled are double-walled and the two walls are annularly interconnected at the inlet end, the annular jacketing chambers thus formed each containing a coaxially inserted baffle tube for guiding the coolant, and the ends of said baffle tubes being fixed in a supplementary tube plate.

United States Patent Ferdinand Market-t Limburgerhoi'; Michael Schunck, Ludwigshalen, both of [72] inventors [54] TUBE PLATE FOR HOT GAS COOLERS 8 Claims, 4 Drawing Figs.

[52] US. Cl 165/142, 263/20 [51] lnt.Cl F28d 7/12 [50] Fleldolsearch 165/140-1411, 164

fmwsw [56] References Cited UNITED STATES PATENTS 826,773 7/1906 Engleitner 165/141 2,372,079 3/1945 Gunter 165/141 2,475,025 7/1949 Huff 165/142 X 2,649,285 8/1953 Brown, Jr. 165/142 X 2,853,277 9/1958 Boni,Jr. et a1... 165/142 X Primary Examiner-Frederick L. Matteson Assistant Examiner-Theophil W. Streule Aiiorney.lohnston. Root. O'Keeffe. Keil. Thompson &

Shurtleff PATENTED 0m 519m SHEET 3 UP 3 FIG. 4

INVIiN'IURS MARKERT HUNCK ATT'YS INAND AEL SC FERD MICH TUBE PLATE FOR HOT GAS COOLERS The invention relates generally to heat exchangers for hot gases and more particularly to a pressure-resistant tube plate for hot gas coolers having tubes provided with additional cooling means at the gas inlet ends.

In many gasification processes the gases produced have high temperatures; they must be cooled before further processing and the sensible heat they contain recovered. In order to prevent substances that may be contained in the gases in a volatilized or dispersed state from being deposited on the heat exchanger surfaces or in order to cool the gases quickly, high gas velocities are often necessary. Moreover, in order to prevent the mechanical strength of such gas coolers from being impaired by excessive thermal stress and corrosive attack, the metal surfaces exposed to the gas stream, particularly the tubes, must not be heated excessively. Difficulties arise particularly in gas coolers in which the gas flows through the tubes and high-pressure steam is to be raised in the outer chamber. The tube plates must then be fairly thick-walled and in standard design it is often impossible to abstract sufficient heat from the ends of the tubes through which the gas enters and which are exposed to the most intensive heating effects.

It has been proposed to protect the inlet ends for instance by sleeves inserted into the tubes, by insulating the tube plate, or by providing, in front of the tube plate, an additional thin nonbearing and separately cooled tube sheet. However, the provision of ceramic or metal sleeves in the tube entries or of insulations in front of the tube plates is usually insufficient. When an additional tube sheet supported by the pressure-resistant main tube plate is provided, it is hardly possible to cause the coolant in the space between the plates to flow in the same direction at all inlet points.

It is therefore the object of the present invention to effectively cool the inlet ends of the tubes arranged in a thick tube plate of hot gas cooler, in which the gas velocities are high and which may in addition be exposed to high corrosive and/or erosive attack, by means of a coolant flowing evenly along a well-defined path.

According to the present invention this is achieved by a tube plate wherein the tubes conveying the gas to be cooled are double-walled forming a jacket around each tube, the two walls being annularly interconnected to close the jacket at the gas inlet ends of the tubes, and baffle tubes are inserted in the annular jackets and secured in a supplementary tube sheet. The space surrounding these baffle tubes between the supplementary tube plate and the load-bearing tube plate facing the gas chamber may communicate with the outer chamber in the hot gas cooler or the jacketing chamber may be closed at both ends, in which case a special coolant may be admitted thereinto and withdrawn therefrom through separate pipes.

Other features of the invention will be understood from the following description with reference to the drawings which diagrammatically illustrate embodiments of the invention.

FIG. I is a cross section of the tube plate on the gas inlet side of a cooler for hot gases. The tube plate 1 is contained in a shell provided with a flange at each end. Flange A connects the shell to gasifying chamber and flange B provides the connection to a cooling chamber or waste heat boiler. The design of the cooling chamber or waste heat boiler with its heat exchanging surfaces in the form of tube coils or the like does not form part of the present invention. Lengths of tube 2 are fitted into the tube plate I by suitable conventional means. These tube lengths project from the plate in a direction contrary to the direction of flow of the gas stream entering the hot gas cooler from the gasification chamber. The tubes 3 through which this gas stream flows are coaxially inserted into the tube lengths 2 so that lengths of double-walled tubes or, in other words, narrow annular cavities or jackets C are formed. The free ends of the two tubes 2 and 3 defining this jacket are drawn together and welded to close the jacket at this end. From the ends remote from the gasification chamber baffle tubes 4 are coaxially inserted into the annular jackets C and fitted into a supplementary plate 5 spaced away from the tube plate I. The free ends of the baffle tubes 4 inside the jackets terminate a short distance away from the interconnected ends of tubes 2 and 3 and thus leave an opening at this point for the passage therethrough of the coolant.

The interconnected tube ends which constitute the inlets for the hot gas entering the tubes 3 may have varying cross sections. In the embodiment according to FIG. 2 only the inlet end of the tube 3 which enters the cooling chamber or waste heat boiler is shaped by being flared towards the larger diameter length of tube 2 and connected thereto, so that a fairly sharp annular edge having the diameter of the length of tube 2 is formed. On the other hand, in the embodiment according to FIG. 3 both the end of the length of tube 2 and that of its associated gas tube 3 are rounded to form a toroidal configuration which improves the abstraction of heat and the conditions of flow outside and inside the tubes. The toroidal configuration of the connection between the tube length 2 and the gas tubes 3 also permits the wall thickness in the region of the connection to be reduced. Finally, the connection shown in FIG. 3 may be made by welding prefabricated toroidal rings to the ends of the tubes 2 and 3. These rings may consist of special high-temperature resistant materials.

The liquid that is to be evaporated or some other coolant is introduced into the space D between the tube plate I and the supplementary plate 5. This fluid will then flow between the tube lengths 2 and the baffle tubes 4 to the interconnected ends of the tubes 2 and 3 and then return between the gas pipes and the battle tubes into the external chamber of the hot gas cooler. In order to raise the tangential velocity of the coolant along the surfaces that are to be cooled, baffles 6 resembling guide blades may be affixed to the ends of the baffle tubes 4 to generate a vortex type of flow about the axis of each tube 3 in its inlet region.

The proposed design of the tube plate and of the inlets ends of the tubes 3 can be further improved by other structural features. Excessive heating of the thick tube plate I can be prevented by allowing the tube length 2 to project far enough into the gas chamber. Moreover, in the spaces between the projecting tube lengths 2 a composition 8 rammed into place or shaped bricks may be provided to form an insulation. For holding the composition in place the tube lengths 2 are advantageously provided with radial studs or other conventional anchoring elements.

In extreme cases the heat flux at the entry into the flue gas tubes may be so high that excessive heating at these points can be prevented only by using a coolant having a fairly low temperature. In a tube plate according to FIGS. l to 3 this could be done for instance by using cold boiler feedwater for cooling the inlet portions. However, this could consume high-mm perature heat for further heating the feedwater and this heat would no longer be available in chamber E for raising steam.

A coolant having a very low temperature may nevertheless be used without adverse effect on steam generation if the annular jackets C do not communicate with the outer chamber E of the heat exchanger and separate flow channels are provided for the admission and discharge of a coolant in natural or forced circulation. For this purpose the pipes which carry the colder coolant out of the annular jackets are preferably taken through the outer chamber E of the heat exchanger.

FIG. 4 is a longitudinal section of a hot gas cooler incorporating this feature. Each of the baflle tubes 4 which are coaxially inserted into the annular jackets is connected by a web 50 to the associated tube length 2. The ends of the baffle tube 4 terminate just short of the ends of the annular jacket C and thus determine the cross section of flow available to the colder coolant which enters through pipe 6 and leaves through pipe 7 for cooling the points of entry of the gas into the flue gas tubes 3 independently of the heat exchange in chamber E. The outlet pipes 7 for the colder coolant may extend a short distance through the chamber for the warmer coolant. The heat thus transferred assists natural circulation through the pipes 6 and 7.

However, the quantity of heat absorbed by the colder coolant in the annular jackets C should preferably be limited,

since it reduces the temperature level of the heat recoverable in chamber E. Consequently, in this embodiment the separately cooled portion of the tube 2 should not be longer than is necessary to provide adequate protection to the flue gas tubes 3. It may be useful to vary the lengths of the tubes 2 which form the cooling jackets and/or to stagger the points of entry of the gas into the flue gas tubes 3 in the axial direction.

We claim:

1. A tube plate adapted for use in a hot gas cooler in which the pressure difl'erential between the gas and the coolant is high and which serves for cooling hot gases flowing at high velocity through the gas-conveying tubes, which comprises a tube-mounting plate, a plurality of gas-conveying tubes mounted in and extending through said plate, the gas-inlet ends of said gas-conveying tubes being double-walled and forming an annular jacket around each tube, the two annular walls thereof being annularly interconnected to close the respective jackets at the gas inlet ends of said tubes, the jacketed portion ol'said tubes projecting beyond the upstream plane of said tube plate. and battle tubes coaxially mounted in respective annular jackets and terminating in spaced relationship to the annular interconnection of the respective gas inlet ends of said gas-conveying tubes.

2. A tube plate as claimed in claim I, a supplementary tube sheet downstream from said tube plate, said gas-conveying tubes extending through respective openings in said tube sheet, and said baflle tubes respectively being mounted in said openings with an annular space between respective gas-conveying tubes and baflle tubes, said annular spaces respectively communicating said jackets and the space between said tube sheet and said tube plate.

3. A tube plate as claimed in claim 1, said jackets being closed at each end, and pipe means for admitting to and withdrawing from said jackets a coolant fluid.

4. A tube plate as claimed in claim 3 wherein said pipe means for withdrawing said coolant fluid are vertical riser pipes.

5. A tube plate as claimed in claim 1, the respective annular interconnections at the inlet ends of said tubes being toroidally rounded.

6. A tube plate as claimed in claim 5 wherein the toroidally rounded interconnections have a wall thickness less than the wall thicknesses of said jacket.

7. A tube plate as claimed in claim 1 wherein the spaces between said respective jacketed portions of said tubes which project beyond the upstream plane of said tube plate are packed with an insulating material.

8. A tube plate as claimed in claim 1, means for introducing a coolant fluid communicating with the annular space between said baffle tubes and the respective outer wall of said jacket, and means for withdrawing said coolant fluid via the annular space between said baffle tube and said gas-conveying tube. 

1. A tube plate adapted for use in a hot gas cooler in which the pressure differential between the gas and the coolant is high and which serves for cooling hot gases flowing at high velocity through the gas-conveying tubes, which comprises a tube-mounting plate, a plurality of gas-conveying tubes mounted in and extending through said plate, the gas-inlet ends of said gasconveying tubes being double-walled and forming an annular jacket around each tube, the two annular walls thereof being annularly interconnected to close the respective jackets at the gas inlet ends of said tubes, the jacketed portion of said tubes projecting beyond the upstream plane of said tube plate, and baffle tubes coaxially mounted in respective annular jackets and terminating in spaced relationship to the annular interconnection of the respective gas inlet ends of said gas-conveying tubes.
 2. A tube plate as claimed in claim 1, a supplementary tube sheet downstream from said tube plate, said gas-conveying tubes extending through respective openings in said tube sheet, and said baffle tubes respectively being mounted in said openings with an annular space between respective gas-conveying tubes and baffle tubes, said annular spaces respectively communicating said jackets and the space between said tube sheet and said tube plate.
 3. A tube plate as claimed in claim 1, said jackets being closed at each end, and pipe means for admitting to and withdrawing from said jackets a coolant fluid.
 4. A tube plate as claimed in claim 3 wherein said pipe means for withdrawing said coolant fluid are vertical Riser pipes.
 5. A tube plate as claimed in claim 1, the respective annular interconnections at the inlet ends of said tubes being toroidally rounded.
 6. A tube plate as claimed in claim 5 wherein the toroidally rounded interconnections have a wall thickness less than the wall thicknesses of said jacket.
 7. A tube plate as claimed in claim 1 wherein the spaces between said respective jacketed portions of said tubes which project beyond the upstream plane of said tube plate are packed with an insulating material.
 8. A tube plate as claimed in claim 1, means for introducing a coolant fluid communicating with the annular space between said baffle tubes and the respective outer wall of said jacket, and means for withdrawing said coolant fluid via the annular space between said baffle tube and said gas-conveying tube. 